An immunochromatographic test strip has a color region preliminarily coated with a bandlike coating of an antibody (or antigen) which brings about an antigen-antibody reaction with an antigen (or antibody) in analyte. When the antigen (or antibody) in analyte labeled with a dye is developed to the color region of the test strip by a developing solution, the antigen (or antibody) in analyte undergoes the antigen-antibody reaction with the bandlike coating of the antibody (or antigen) to be trapped, thus forming a colored line of color caused by the dye in the color region.
With the immunochromatographic test strip of this type, the amount of the antigen (or antibody) in analyte can be quantitatively determined by optically measuring the color intensity of the colored line formed in the color region, by means of a measuring device.
As a device for measuring the color intensity of the test strip such as the immunochromatographic test strip, there is a conventionally well-known device configured to irradiate measurement light onto the colored line (color zone) formed in the color region of the test strip and to receive reflected light thereof to measure the color intensity of the colored line (e.g., reference is made to Patent Document 1 and Patent Document 2).
[Patent Document 1] Japanese Patent Application Laid-Open No. 11-326191
[Patent Document 2] Japanese Patent Application Laid-Open No. 11-83745